Question

13a. For an object's mechanical energy to be conserved, what condition must be satisified? Group of answer choices There is no fore acting on the object. There is no friction force acting on the object There is only conservative forces acting on the object. There is only conservative forces doing work on the object.

b.The SI unit of the spring constant k is _________. (You may need to check your textbook for the answer.) Group of answer choices N N/m J/m J

c. Is the following statement true or false? The SI unit of kinetic energy and potential energy is the same. Group of answer choices True False

d. Is the following statement true or false? A spring stretched by 5cm stores the same potential energy as the spring compressed by 5cm. Group of answer choices True False

e. Which of the following is a conservative force? Group of answer choices Frictional force. Tension force in a rope Normal force Spring force

Answer 1

13 a)
When is system's mechanical energy is conserved, the forces acting on the system must be conservative.
Thus there can be forces acting on the system, so the first choice is wrong. Frictional force is a non conservative force, and thus it should not be present when the mechanical energy is conserved. Thus the second choice is correct. The third and fourth choices are also correct as for mechanical energy conserved system, there should be only conserved forces acting on the system and conservative forces only do work
b) As F = - k x
The unit of k, the spring constant should be that of
unit (k) = unit of force / unit of distance
unit of k = N / m
in SI system
c) The SI unit of kinetic energy and potential energy is the same namely Joules (J)
d) The potential energy of the spring is given as
PE = (1/2) k x2
Whether x, the distance from the mean position is positive or negatve (strecthed or compressed ) the potential energy will be the same.